package quene_stack;

import java.util.LinkedList;
import java.util.Queue;

/**
 * 用队列实现栈
 */
class MyStack {

    private Queue<Integer> qu1;
    private Queue<Integer> qu2;

    public MyStack() {
        qu1 = new LinkedList<>();
        qu2 = new LinkedList<>();
    }
    
    public void push(int x) {
        if(!qu1.isEmpty()){
            qu1.offer(x);
        }else if(!qu2.isEmpty()){
            qu2.offer(x);
        }else{
            qu1.offer(x);
        }
    }
    
    public int pop() {
        if(empty()){
            return -1;
        }
        int ret = -1;
        if(!qu1.isEmpty()){
            int size = qu1.size();
            for(int i = 0; i < size - 1; i++){
                int temp = qu1.poll();
                qu2.offer(temp);
            }
            ret = qu1.poll();
        }else{
            int size = qu2.size();
            for(int i = 0; i < size - 1; i++){
                int temp = qu2.poll();
                qu1.offer(temp);
            }
            ret = qu2.poll();
        }
        return ret;
    }
    
    public int top() {
        if(empty()){
            return -1;
        }
        int temp = -1;
        if(!qu1.isEmpty()){
            int size = qu1.size();
            for(int i = 0; i < size; i++){
                temp = qu1.poll();
                qu2.offer(temp);
            }
        }else{
            int size = qu2.size();
            for(int i = 0; i < size; i++){
                temp = qu2.poll();
                qu1.offer(temp);
            }
        }
        return temp;
    }
    
    public boolean empty() {
        return qu1.isEmpty() && qu2.isEmpty();
    }
}